Apparatus for pressing objects out of thermoplastic material, and particularly phonographic disks

ABSTRACT

A press frame supports upper and lower plates having opposed surfaces with a pattern on each. The upper plate is secured to an ultrasonic vibration means, upward movement of which is resisted by resiliently flexible means. The lower plate is connected to a pressure fluid actuated device for urging, at a low or a high pressure, the lower plate against the upper plate when a plastic material is therebetween, thereby forming an impression in said material.

United States Patent Renoux Aug. 14, 1973 APPARATUS FOR PRESSING OBJECTSOUT 3,166,617 1/1965 Munk 4251424 x OF THERMOPLAS'HC MATERIAL AND3,456,295 7/1969 Torigai et a1. 425/ 174.2 X 2,622,301 12/1952 Argarden425/424 PARTICULARLY PHONOG DISKS 3,178,792 4/1965 Scott 4251407 x [76]Inventor: Robert A. Renoux, Les Cles de la 3,635,622 1/1972 Wecksler425/408 X Foret, 80, avenue, Lefebvre Poissy, France PrimaryExaminer-Robert L. Spicer, Jr. [22] Filed; o 18, 1971Attorney-Woodharns, Blanchard & Flynn [211 App]. No.: 189,965

. [57] ABSTRACT 52 U.S. Cl 425/174.2, 425/354, 425/385, A Pfess frameSupports PW and Plates-having 425/408 425/424 opposed surfaces with apattern on each. The upper 51 Int. Cl. B290 3/06, B06b 3/00 Plate issecured to an ultrasonic vibration means, "P- 5 n w f Search 425/1741742 3 5 4 ward movement of which is resisted by resiliently flexi-425/363, 408, 424, 456, 335, 407, 470, DIG ble means. The lower plate isconnected to a pressure 35 fluid actuated device for urging, at a low ora high pressure, the lower plate against the upper plate when a [56]Reference cu plastic material is therebetween, thereby forming an UNITEDSTATES PATENTS impression in said material.

9/ i946 Lindkwist 425/456 UK 8 Claims, 3 Drawing Figures Patgnted Aug.14, 1973 3,752,620

2 Sheets-Sheet 1 Patented Aug. 14, 1973 2 Sheets-Sheet 2 APPARATUS FORPRESSING OBJECTS OUT OF THERMOPLASTIC MATERIAL, AND PARTICULARLYPHONOGRAPHIC DISKS The presentinvention concerns a method and anapparatus for pressing objects out of thermoplastic material,particularly phonographic disks, wherein the previously heated materialis compressed.

It is known that the manufacture of precision molded products, such asphonographic diSks, from thennoplastic material calls for a successionof delicate operations because of the elements comprising the productioncycle, namely, the treatment of the material, pressing, steam, water forcooling, etc.

In spite of the improvements made during recent years in the specialinjection presses, the existing conditions at the moment of pressing arenot always the same, which results in variations in the production and,consequently, a significant loss. In particular, no precise control canbe exercised on the temperature of the material at the moment ofpressing, so that one is generally obliged to lengthen uselessly theduration of the cycle, which obviously reduces the speed of production.

It is the principal purpose of the present invention to remedy thisinconvenience and, in order to do this, it has for its object a pressingmethod of the abovementioned type consisting in subjecting the materialunder pressure to a complementary regulated heating by means of highfrequency vibration, notably ultrasonic, during a phase preceding thefinal pressing.

Thus, because of the use of ultrasonic or of another analogous vibratorymeans, such as hyperfrequencies, a very precise and extremely rapidheating can be obtained for the thermoplastic material and effectedwhile the latter is under pressure. Further, the vibratory effect oftheultrasonic improves the formation of the impression, that is, in thecase of disks, the penetration of the material into the grooves of themaster or pattern. After having interrupted the ultrasonic vibration,the pressing is continued for a few moments, advantageously under highpressure, so as to overcome the vibratory effect. One proceeds next tocongeal the molded piece by a sudden cooling which relieves the internalstresses.

The heating by ultrasonic vibration or by other high frequencyvibrations having no inertia, in contrast to heating by steam, generallyused until now, it is seen that with the procedure according to theinvention, the speed of production can be considerably increased.Further, as the supply of heat can be controlled with great precision,the molding can still be completely effective taking into account thethermoplastic material used.

Preferably, the complementary heating is carried out with a pressurelower than kg/cm, the final pressing being made with a pressure higherthan 5 kg/cm.

It has been found, in fact, that pressures higher than 5 kg/cm wouldovercome the vibratory effect of the ultrasonic device and,consequently, cut off the supply of heat as well as the advantagesrelating to the congealing of the molded article.

An apparatus for carrying out the process according to the inventioncomprises two disks disposed opposite to each other, each one bearinghalf of a pattern, and the first disk is shown as movable transverselyin the direction toward the second disk. Said first disk is subjected tothe reaction of a resiliently flexible means and said first disk isintegral with at least one transmitter of high frequency vibrations. Thesecond disk is provided with circulation channels for cooling fluid andis movable transversely by the actuating means capable of fur nishing,at the proper time, the low pressure needed to balance the force exertedby the resiliently flexible means, during the functioning of thevibration transmitter, and the high pressure necessary for the finalpressing of the material.

In one particular embodiment of the invention, the first plate isintegral with several high frequency vibration transmitters and containssome radial grooves separating the different zones of effectiveness ofthese transmitters.

Two forms of carrying out the invention are de scribed hereinafter byway of example, and by reference to the attached drawings, in which:

FIG. I is a partially sectioned view of a pressing or molding apparatusconforming to the invention;

FIG. 2 is a partially sectioned view of a modification for carrying outthe invention, equipped with several ultrasonic transducers;

FIG. 3 is a sectional view taken along the line III-III of FIG. 2; and

FIG. 4 is a sectional view taken along the line IV--IV of FIG. 3.

The pressing apparatus disclosed in FIG. 1 is especially designed forthe manufacture of phonographic disks, rigid or flexible, and comprisesfirst of all two circular, horizontally disposed plates 1 and 2, whichare disposed opposite each other, said plates carrying halves 3 and 4 ofthe pattern, respectively.

The lower plate 1 carrying the half 3 of the pattern is provided withcircular channels 5 for a cooling fluid and it is affixed to a platesupport 6 by the screws 7. It will be noted on the other hand. that theplate 1, is equipped with a device 8 of a known type,'arranged to formthe central opening in the phonographic disk while it is being pressed.

The plate support 6 is attached in turn by the screws 9 to a piston 10,with a flexible joint 30 therebetween permitting the take-up of defectsin the meeting faces of plates 1 and 2. The piston 10 is capable ofsliding vertically in a cylindrical bore 1 I provided in a base 12 bythe force of a pressure fluid applied through an input orifice 13furnished from a source of supply S, which inturn has a conventionalcontrol device C associated therewith for controlling the pressure ofthe fluid supplied to the bore 11. This piston It) is surrounded with anannular liquid tight seal 14, maintained in place by a lock ring 15which is secured to the body 12 by the screws 16.

The top plate 2, which carries the other half 4 of the pattern, isindirectly supported by a horizontal plate support 17 which is securedby the screws 18 to the upper parts of two side plates 19, which areaffixed at their lower ends to the base 12 by the screws 20. On theplate support 17 is fixed by soldering a central sleeve 21 in theinterior of which is disposed, according to the invention, a highfrequency vibration transmitter, comprised here by an ultrasonictransducer 22 the lower part 23 of which passes through an opening 24 inthe plate 17 and is integrally attached to the plate 2 by a threadedconnection.

The transducer 22 is engaged by some pointed screws 25, furnishingsupport at the node of vibrations, which screws are mounted on a ring 26susceptible to upward sliding movement within the interior of the sleeve21. Furthermore, this transducer and plate 2, to which it is fixedlysecured, are constantly urged toward the base 12 by a helical spring 27engaged at its lower end by the sliding ring 26 and on the upper end bya ring 28 which is screwed within the upper end of the sleeve 21. Thisring 28 is thus adjustable in height and permits, as a result, preciseadjustment of the resilient force exerted by the spring 27. It will benoted moreover that this ring 28 furnishes a suitable opening to receiveone of the extremities of a tube 29, designed to convey a cooling fluid,such as air, to the ultrasonic transducer 22.

The pressing apparatus which has been described functions in thefollowing manner:

The thermoplastic material to be molded, which ought to be in the formof granules or in cut plastic film, undergoes the first step of heatpreparation and is thereafter brought, by any known mechanical means orelse by injection, between the patterns 3 and 4 carried by the plates 1and 2. The ultrasonic transducer 22 is then excited by a high frequencycurrent, delivered by a generator (not shown) simultaneously as thelower plate 1 is raised toward the upper plate 2 by means of piston 10.

When the patterns 3 and 4 come into contact with the plastic materialtherebetween, the upper plate 2 is pushed upwardly, to bring into effectthe action of the spring 27, and then attains a position of equilibriumin which the downward force exerted by the spring 27 is in balance withthe force exerted upwardly by the piston 10 on the lower plate 10. Thethermoplastic material thus becomes subjected to a first pressure, whichis relatively low and, moreover, can be adjusted by means of ring 28.

During this first phase of pressure, the ultrasonic movement of thetransducer 22 causes the equalized heating of the pattern. It isunderstood, thus, that in adjusting the frequency and duration of thefunctioning of the transducer, one is able to effect a perfectlyregulated complementary heating control of the material, and this withextreme precision. The pressing conditions are thus precisely determinedand one can quickly complete the molding takinginto account thecharacteristics the materials used. Furthermore, the vibratory effect ofthe ultrasonic. device improves the setting of the impression byfacilitating the penetration of the material into the bottom of thegrooves of the pattern, where a phonographic disk is involved.

After a predetermined time of pressing, at low pressure, the functioningof the transducer 22 is terminated, and the pressing or molding isfollowed, for a short period of time, by a greater pressure in order toterminate the effect of the ultrasonic vibrations. In the course of thisphase of high pressure, the upper plate 2 naturally comes to bearagainst plate support 17 under the force of piston 10 which is exertednow on the lower plate 1 by a strong corresponding pressure. Thereafter,a cooling fluid, such as water, is caused to flow in the circulargrooves of the plate 1 for congealing the molded object and removing allthe internal stresses. Likewise, it is observed that, in the course ofoperation, the transducer 22 is cooled by a flow of air conveyed by thetube 29.

As the ultrasonic heat has no inertia, it is easily understood that thespeed of production of such an apparatus of pressing can be very high,without any reduction in the quality of the molded objects. By way ofexample, it is only in the neighborhood of a few hundredths of a secondto raise the temperature of the thermoplastic temperature to more thanC, at the same time being sufficient to bring all of it to a standardtemperature.

It is observed, in addition, that pressures greater than 5 kg/cmovercome the ultrasonic vibratory effect and, consequently, theapplication of heat. Consequently the plates carrying the pattern aresubjected, during the first phase of pressing to a lower pressure than 5kg/cm, a phase in the course of which a thermoplastic material willundergo a complementary heating controlled by the ultrasonic vibrationscreated by the transducer 22.

When the necessary temperature shall have been attained, the functioningof the transducer will be terminated while the pressing will be followedwith a strong pressure in excess of 5 kg/cm for example, in the order of50 kg/cm. The means of supplying the fluid to the piston 10 will beunderstood to be such as to permit the application by the piston of thetwo different pressures required.

In the modified embodiment disclosed in the FIGS. 2 to 4, the upperplate 2 is equipped with several identical transducers 22, four in thisexample, of which the lower extremities 23 are uniformly disposed in acircle around this plate. In this mode of disclosure, the fourtransducers 22are supported, as previously described, by means ofpointed screws 25 on a ring 26 capable of being displaced upwardly in ahollow cylinder 32 defined within the plate support 17. This ring 26 isaffixed to another ring 33 integral with a central sleeve 34, mountedfor sliding on a vertical axle 35 integral with the plate support 17.The transducers 22 are urged to ward the lower plate support 6 by aresilient spring 36 which is here disposed around the axle 35 andengaged at its lower end by the sleeve 34 and at its upper end by a ring37 held on the upper threaded end of the axle 35 by the threaded lockingcollar 38. This locking collar 38 permits the adjustment of the highestposition of the ring 37 and consequently the adjustment, as previouslystated, to compensate for pressure exercised by the resilient spring 36during the operation of the ultrasonic device.

The upper part of the apparatus is covered by a protective case 39furnished with a lateral opening 40 forming an opening which is providedwith an air tube 41 permitting the cooling of the transducer 22 in thecourse of its operation.

Conforming to a peculiarity of the invention, the upper plate 2 isdivided into four sections by the radial grooves 42, as shown in theFIGS. 3 and 4, in order to separate clearly the different zones ofinfluence of the four transducers 22 and to avoid useless interference.

It will be seen, moreover, that one can conceive of numerousmodifications in details from the examples disclosed and described,without exceeding the scope of the invention.

We claim:

1. An apparatus for pressing an object, such as a phonographic disc,from thermoplastic material, said apparatus comprising:

frame means;

first plate means movably mounted on said frame means for rectilinearmovement relative thereto said frame means including abutment meansnormally spaced from first plate means and disposed for engagement bysaid first plate means when same is moved away from the predeterminedposition in a second direction which is opposite said first direction;

high frequency vibrating means connected to said first plate means forpermitting selected vibration thereof;

second plate means movably mounted on said frame means for rectilinearmovement relative thereto and relative to said first plate means along asecond line of movement which is substantially parallel to said firstline of movement, said segond plate means having a second pressing facethereon which is normally disposed opposite but spaced from said firstpressing face;

fluid pressure cylinder means mounted on said frame means and coactingwith said second plate means for moving same relative to said framemeans toward said first plate meansf and control means for supplyingpressure fluid to said fluid cylinder means for causing linear movementof said second plate means toward and into engagement with said firstplate means, whereby the opposed pressing faces are able to form anobject therebetween, said control means initially supplying pressurefluid to said cylinder means at a first pressure level so that saidsecond plate means moves into engagement with said first plate means andmoves same away from said predetermined position in opposition to theurging of said resilient means so that the forces exerted on the firstand second plate means by the cylinder means and the resilient means aresubstantially equalized, said control means then supplying pressurefluid to said cylinder means at a second pressure level which issubstantially greater than said first pressure level for causing furtherdisplacement of said second plate means toward said first plate meansfor causing said first plate means to be moved into engagement with saidabutment means for causing pressing of the material contained betweenthe opposed pressing faces.

2. An apparatus according to claim 1, wherein said vibrating meanscomprises an ultra-sonic transducer having a portion thereof fixedlyconnected to said first plate means for causing high frequency vibrationthereof when the first and second plate means are in engagement withanother due to the presence of pressure fluid at said first pressurelevel within said cylinder means, said high frequency vibration causingheating of the material disposed between the opposed pressing faces.

3. An apparatus according to claim 2, wherein said vibrating meansfurther includes a support member slidably supported on said frame meansand having means fixedly mounted thereon and disposed in supportingengagement with said transducer at the node of vibration thereof, andsaid resilient means comprising spring means coacting between said framemeans and said support member for urging said support member intoabuting engagement with a stop surface formed on said frame meanswhereby said first plate means is normally maintained in saidpredetermined position.

4. An apparatus according to claim 2, wherein said transducer issubstantially aligned with the central longitudinally extending axis ofsaid first plate means and is fixedly connected to said first platemeans substan tially at the midpoint thereof, and said resilient meansincluding a spring member disposed in surrounding relationship to saidtransducer.

5. An apparatus according to claim 2, wherein said vibrating meansincludes a plurality of substantially identical transducers disposedsubstantially parallel to one another and having one end of each fixedlyconnected to said first plate means, said plurality of transducersbeingdisposed within a circular pattern generated substantially aboutthe central longitudinally extending axis of said first plate means.

6. An apparatus according to claim 5, wherein said first plate means hasa plurality of radially extending grooves formed therein for separatingsaid first plate means into a plurality of different zones, each of saidzones having a different one of said transducers connected thereto.

7. An apparatus according to claim 1, wherein each of said pressingfaces has pattern means formed thereon defining one side of aphonographic disc.

8. An apparatus according to claim 7, wherein said second plate meanshas passage means formed therein for permitting circulation of a coolingfluid therethrough. i V

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION .3 Patent No. '3752 620 Dated August 14, 1973 Inventor(s) Robert A. Renoux It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

' Foreign Application Priority Data Oct. 20, 1970 France .....70.37736Column 5, line 10, after "from"; insert said Signed and sealed this 7thday of May 1971;.

SEAL) Attest:

V EDl-JAHD I-LFLETCiiEf-i, J R. C. MARSHALL DANN Attesting OfficerCommissioner of Patents FORM PO-IOSO (10 69) USCOMWDC 6037M,"

- U. S. GO VERNMINT PRINTING OFFICE "l. OJl-33"

1. An apparatus for pressing an object, such as a phonographic disc,from thermoplastic material, said apparatus comprising: frame means;first plate means movably mounted on said frame means for rectilinearmovement relative thereto along a first line of movement, said firstplate means having a first pressing face thereon; resilient meanscoacting between said frame means and said first plate means fornormally resiliently urging said first plate means in a first directionfor normally maintaining said first plate means in a predeterminedposition relative to said frame means; said frame means includingabutment means normally spaced from first plate means and disposed forengagement by said first plate means when same is moved away from thepredetermined position in a second direction which is opposite saidfirst direction; high frequency vibrating means connected to said firstplate means for permitting selected vibration thereof; second platemeans movably mounted on said frame means for rectilinear movementrelative thereto and relative to said first plate means along a secondline of movement which is substantially parallel to said first line ofmovement, said second plate means having a second pressing face thereonwhich is normally disposed opposite but spaced from said first pressingface; fluid pressure cylinder means mounted on said frame means andcoacting with said second plate means for moving same relative to saidframe means toward said first plate means; and control means forsupplying pressure fluid to said fluid cylinder means for causing linearmovement of said second plate means toward and into engagement with saidfirst plate means, whereby the opposed pressing faces are able to forman object therebetween, said control means initially supplying pressurefluid to said cylinder means at a first pressure level so that saidsecond plate means moves into engagement with said first plate means andmoves same away from said predetermined position in opposition to theurging of said resilient means so that the forces exerted on the firstand second plate means by the cylinder means and the resilient means aresubstantially equalized, said control means then supplying pressurefluid to said cylinder means at a second pressure level which issubstantially greater than said first pressure level for causing furtherdisplacement of said second plate means toward said first plate meansfor causing said first plate means to be moved into engagement with saidabutment means for causing pressing of the material contained betweenthe opposed pressing faces.
 2. An apparatus according to claim 1,wherein said vibrating means comprises an ultra-sonic transducer havinga portion thereof fixedly connected to said first plate means forcausing high frequency vibration thereof when the first and second platemeans are in engagement with another due to the presence of pressurefluid at said first pressure level within said cylinder means, said highfrequency vibration causing heating of the material disposed between theopposed pressing faces.
 3. An apparatus according to claim 2, whereinsaid vibrating means further includes a support member slidablysupported on said frame means and having means fixedly mounted thereonand disposed in supporting engagement with said transducer at the nodeof vibration thereof, and said resilient means comprising spring meanscoacting between said frame means and said support member for urgingsaid support member into abuting engagement with a stop surface formedon said frame means whereby said first plate means is normallymaintained in said predetermined position.
 4. An apparatus according toclaim 2, wherein said transducer is substantially aligned with thecentral longitudinally extending axis of said first plate means and isfixedly connected to said first plate means substantially at themidpoint thereof, and said resilient means including a spring memberdisposed in surrounding relationship to said transducer.
 5. An apparatusaccording to claim 2, wherein said vibrating means includes a pluralityof substantially identical transducers disposed substantially parallelto one another and having one end of each fixedly connected to saidfirst plate means, said plurality of transducers being disposed within acircular pattern generated substantially about the centrallongitudinally extending axis of said first plate means.
 6. An apparatusaccording to claim 5, wherein said first plate means has a plurality ofradially extending grooves formed therein for separating said firstplate means into a plurality of different zones, each of said zoneshaving a different one of said transducers connected thereto.
 7. Anapparatus according to claim 1, wherein each of said pressing faces haspattern means formed thereon defining one side of a phonographic disc.8. An apparatus according to claim 7, wherein said second plate meanshas passage means formed therein for permitting circulation of a coolingfluid therethrough.